The KEF Blade uses a large rubber front piece and rubber bushings that decouples it from the chassis itself. The loudspeaker cookbook recommends well nuts. What are some other ways to mechanically decouple different parts of a speaker?
It is unwise to randomly add resilient materials to an assembly without knowing what the resonant frequency of the resulting spring/mass system becomes!
Those would have to be some strong magnets. That and wouldn't you still need to worry about sealing the enclosure?
If memory serves, I think the idea isn't so much resilience as much as something like CLD - using a softer material between two harder materials in order to reduce the transfer of energy between parts.
Ah I see what you mean now. Did you have any issues with any resonances? If I'm looking at this correctly, that speaker is kinda just dangling from something lol
The polyurethane sealant used as adhesive is quite sturdy although it remains flexible, and it's very sticky to begin with although difficult to deal with.
The magnet is close to the effective grounding point of the driver. Mounting this way can bypass the basket resonance.
The magnet is close to the effective grounding point of the driver. Mounting this way can bypass the basket resonance.
So then that back part is it's "ground" since it's not load bearing. Neat approach. Definitely gives me some ideas.
I see what you mean now. https://assets.kef.com/documents/reference/KEF_Blade_Ref_Meta_Tech_Paper.pdf decided to look up the paper for the blade. So even the "softer" material needs to have good resonant properties. Although that does give me an idea. Maybe an external bracket with a decopler like a rubber gasket or maybe even zorbithane (very conservative use of zorbithane because that stuff is stupid expensive)
Yes pretty much something like that. Glad to know my idea has already been tested. What's the model?
Q Acoustics Concept 30. There's a white paper on it and some of the blurb.
The drive units are fixed to a double radius, highly stiff, 3mm thick, damped aluminium baffle plate which has been designed both in material and form. Studs, extending from the back of the drive unit chassis pass through the stiff P2PTM cross-braces and provide the fixings for this baffle assembly. The studs are pretensioned to give the correct cabinet acoustic seal whilst minimising the structural coupling of the baffle assembly in the main cabinet assembly.
In addition to the smooth low acoustic diffraction profile of the baffle, the geometric curvatures provide high stiffness for relatively low material mass, thus pushing the fundamental baffle resonance well away from the main excitation of the woofer. The tweeter is dynamically isolated from the baffle.
Tweeter is built on a die-cast chassis which is fully hermetically sealed and mechanically isolated (floating) from the front baffle.
The drive units are fixed to a double radius, highly stiff, 3mm thick, damped aluminium baffle plate which has been designed both in material and form. Studs, extending from the back of the drive unit chassis pass through the stiff P2PTM cross-braces and provide the fixings for this baffle assembly. The studs are pretensioned to give the correct cabinet acoustic seal whilst minimising the structural coupling of the baffle assembly in the main cabinet assembly.
In addition to the smooth low acoustic diffraction profile of the baffle, the geometric curvatures provide high stiffness for relatively low material mass, thus pushing the fundamental baffle resonance well away from the main excitation of the woofer. The tweeter is dynamically isolated from the baffle.
Tweeter is built on a die-cast chassis which is fully hermetically sealed and mechanically isolated (floating) from the front baffle.
Here are some ideas on how to isolate vibration; the first is a "box in a box" design, the Bass driver an cone tweeter are in there own enclosures, numbered 1 and 2, (the bass vented to the main enclosure, they fit in through a trapdoor in the bottom, are held in place by spring plunger things (marked 3) against foam gaskets on the inside of the front baffle. The second is similar to the construction of the BBC LS35a, in that the drivers are held on the front baffle, which is isolated and damped from the main enclosure by a soft gasket - instead of screws used in the BBC design I used tension springs to hold the front baffle on, and screws to hold the rear panel on. The third used drivers mounted back to back in a dumbbell thing, which slides in the main enclosure from the rear, is suspended by foam/carpet tile, and is held in by a rear cover. the last, I just bolted 4.5 kg lumps of cast iron to the speaker magnets.
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I'd like to share a story about the 'miracle' Sorbothane material when it became available for walking boot insoles in the '80s.
Outdoor shops were supplied a thick slab of the stuff and a large wooden mallet, supposedly to demonstrate to customers that it absorbed all vibration, by holding the slab in one hand and hitting it with the mallet held in the other, resulting in a nice dull thud.
Ever the sceptical physicist, I asked if he'd like to try the same experiment by placing his balls on an anvil, Sorbothane on top of them, and whacking it with said large mallet. Application matters...
No mechanical 'isolator', whether rubber/spring-damper/high mass will isolate all frequencies. They all have a specific resonant point (plus a Q and a damping frequency response) which needs to be known for a specific application.
Compare a 60's Citroen 2CV with a current Formula One car - they are both brilliant at the specific job for which they were designed, which were utterly different!
Outdoor shops were supplied a thick slab of the stuff and a large wooden mallet, supposedly to demonstrate to customers that it absorbed all vibration, by holding the slab in one hand and hitting it with the mallet held in the other, resulting in a nice dull thud.
Ever the sceptical physicist, I asked if he'd like to try the same experiment by placing his balls on an anvil, Sorbothane on top of them, and whacking it with said large mallet. Application matters...
No mechanical 'isolator', whether rubber/spring-damper/high mass will isolate all frequencies. They all have a specific resonant point (plus a Q and a damping frequency response) which needs to be known for a specific application.
Compare a 60's Citroen 2CV with a current Formula One car - they are both brilliant at the specific job for which they were designed, which were utterly different!
An alternative experiment (I wont try the balls and anvil) is to lie on a bed of nails, and hold a concrete slab on your chest, and have someone smash it with a hammer. A low frequency would result in a lot of holes in your back, but the impulse of the hammer blow doesn't.
Remlab had an interesting thread on using Sorbothane/aluminium layered sandwich front baffle, I think it was called "mid range experiment".
Thank you for the story. I laughed like a moron reading it.
https://www.audiosciencereview.com/forum/index.php?threads/constrained-layer-damping.8229/ This is what originally lead me down the Sorbothane rabbit hole in the first place.
I guess my question then would be; what is the frequency range you're trying to isolate when decoupling something from the main chassis?
https://www.diyaudio.com/community/...adener-and-high-density-acoustic-felt.360772/ This the one?